iio: common: st_sensors: fix channel data parsing

Using realbits as i2c/spi read len, when that value is not byte aligned
(e.g 12 bits), lead to skip msb part of out data registers.
Fix this taking into account scan_type.shift in addition to
scan_type.realbits as read length:

read_len = DIV_ROUND_UP(realbits + shift, 8)

This fix has been tested on 8, 12, 16, 24 bit sensors

Fixes: e7385de5291e ("iio:st_sensors: align on storagebits boundaries")
Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@st.com>
Tested-by: Linus Walleij <linus.walleij@linaro.org>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

2 files changed, 6 insertions, 2 deletions

diff --git a/drivers/iio/common/st_sensors/st_sensors_buffer.c b/drivers/iio/common/st_sensors/st_sensors_buffer.c
index fe7775bb3740..df4045203a07 100644
--- a/drivers/iio/common/st_sensors/st_sensors_buffer.c
+++ b/drivers/iio/common/st_sensors/st_sensors_buffer.c
@@ -30,7 +30,9 @@ static int st_sensors_get_buffer_element(struct iio_dev *indio_dev, u8 *buf)
 
         for_each_set_bit(i, indio_dev->active_scan_mask, num_data_channels) {
                 const struct iio_chan_spec *channel = &indio_dev->channels[i];
-                unsigned int bytes_to_read = channel->scan_type.realbits >> 3;
+                unsigned int bytes_to_read =
+                        DIV_ROUND_UP(channel->scan_type.realbits +
+                                     channel->scan_type.shift, 8);
                 unsigned int storage_bytes =
                         channel->scan_type.storagebits >> 3;
 
diff --git a/drivers/iio/common/st_sensors/st_sensors_core.c b/drivers/iio/common/st_sensors/st_sensors_core.c
index 975a1f19f747..d5cf7f31eaf9 100644
--- a/drivers/iio/common/st_sensors/st_sensors_core.c
+++ b/drivers/iio/common/st_sensors/st_sensors_core.c
@@ -483,8 +483,10 @@ static int st_sensors_read_axis_data(struct iio_dev *indio_dev,
         int err;
         u8 *outdata;
         struct st_sensor_data *sdata = iio_priv(indio_dev);
-        unsigned int byte_for_channel = ch->scan_type.realbits >> 3;
+        unsigned int byte_for_channel;
 
+        byte_for_channel = DIV_ROUND_UP(ch->scan_type.realbits +
+                                        ch->scan_type.shift, 8);
         outdata = kmalloc(byte_for_channel, GFP_KERNEL);
         if (!outdata)
                 return -ENOMEM;